1. Field of the Invention
The invention is in the field of liquid-tight but gas-vented containers. A particular contemplated use is in conjunction with storage batteries.
2. Description of the Prior Art
The use of liquid containing vessels, which vent gas while suppressing the leakage of the liquid, is widespread. For example, lead-acid storage batteries in automotive use generate gases within the electrolyte. As the battery sustains vibration during use, the internally generated gases must be vented and the battery acid must be kept, to a large extent, inside of the battery. Devices which have in the past been developed for this use include caps containing a chamber with a small hole on the fluid side and a small hole on the air side. There are also caps containing baffles of various geometries (e.g., U.S. Pat. No. 4,031,294, issued June 21, 1977). However, under conditions of violent shaking or tipping vessels with such caps are still susceptible to some spillage of the contained liquid.
In order to provide the desired leakage control it is required that the body of the plug or cap be sealed to the wall of the fluid containing vessel. Many plug designs make use of a rubber gasket to make the required seal. Many common rubbers contain constituents which can leach out of the body of the rubber, when in contact with battery acid. Common antiozonants are susceptible to such leaching. This can result in the cracking of the rubber due to ozone attack. In addition, the chemical leached into the battery acid can be deleterious to battery operation. This is particularly troublesome to batteries intended for long service life, such as standby batteries in telephone central offices.